This invention relates generally to valves and more particularly concerns valves of the multi-port type.
Valves presently used in applications for which this device is intended commonly employ a rotating cylinder having side wall apertures of varying diameters. As the cylinder is rotated, the diameter of the aperture aligned with the valve outlet determines the fluid flow rate. Though workable, these valves have several disadvantages.
For effective operation, the fluid flow path from the aperture to the outlet passage must be sealed. Sealing the curved, rotating, cylinder wall against the valve inside wall requires close tolerances. And even if achieved, wear in ordinary use will damage the seal.
Also, since the apertures are drilled in a single cylinder, wear or damage to a single aperture may necessitate replacement of the cylinder.
Furthermore, a single cylinder can only provide a limited number of flow rates in a single sequence. A desired change in one aperture would require a new cylinder, and a reasonable flexibility in rates and sequences could require a large number of cylinders.
This suggests an additional difficulty, the need for a different valve in changing from continuous to intermittant flow operation.
Accordingly, it is an object of the invention to provide a valve for controlling the rate of fluid flow through its outlet passage.
A further object of the invention is to provide a valve minimizing the adverse effects of ordinary wear on its component parts.
It is also an object of the invention to provide a valve having suitable flexibility in choices of flow rates and sequences.
Another object of the invention is to provide a valve readily adaptable for continuous or intermittant fluid flow operation.